This invention concerns a gripping device and particularly, though not exclusively, a device to serve as a pipeline recovery tool or mooring connector.
Devices of this kind are known and described, for example, in patent specification WO 2004/055394 which refers to a mooring connector being a device which is inserted into an anchored receptor, for example on the sea bed, and responds to a pull from a mooring line attached to the connector, by locking together the connector and the receptor.
Alternatively, a pipeline recovery tool may be in the form of a mandrel which is placed inside a pipe and when pulled locks the tool and the pipe together. In some cases, such a tool may be of tubular form to be located around an object to be recovered, again operating such that the tool and the object become interlocked when the tool is pulled.
The device involves so-called ball and taper assemblies, and comprises a pair of elongate members, one of which has an array of ramped surfaces while the other comprises a ball cage with an array of balls interacting with the ramped surfaces such that relative movement of the two elongate members causes the balls to protrude through apertures in the ball cage thus to engage, internally or externally, the pipe or other object to be gripped. In the case of a mooring connector a mooring line is thus connected to a fixed anchor, some means being provided to release the connector from the anchor when required.
In all such devices the ramped surfaces of the mandrel, the apertures of the ball cage, and the balls residing therein, are disposed in longitudinally spaced annular rows around the gripping device. Since the gripping relationship between the device and the object to be gripped involves considerable force, the effect is that the balls tend to become partially embedded within the surface of the object to be gripped with the result that after repeated use of the device, the receptive object displays regular annular grooves created by the rows of balls. It is an object of the present invention to provide a gripping device of this general kind but where such a disadvantage is at least substantially overcome.